Ender Bag: Add per-chunk timeouts. Item chunk load requirement bugged still.

Switching between items and just opening the player inventory messes up
the chunk loading timeouts so that the chunks get stuck loaded.
Ender Bag: (Hopefully) fix the unloading issue. Remove debug prints.
Ender Bag: Add binding and opening Ender Chest. Remove bind if block changed.
Ender Bag: Add icons for regular vs. ender chest bind, and closed vs. open.

The NBT data from PlayerOpenContainerEvent doesn't currently sync to
the client immediately, and thus the bag is left visually open,
until some other change syncs it to the client.